1. Field of the Invention
This invention relates generally to observation windows for observing the contents of a cargo hold in a vessel or the like, and more particularly to a deck mounted sight glass for cargo holds of marine vessels.
2. Description of the Prior Art
For various reasons, during the filling, transport, and emptying of cargo holds, it is desirable to inspect the interior thereof. For cargo holds on barges, the typical practice is to provide a sight glass in the deck or in a hatch. It is quite common for such sight glasses to become partially or entirely occluded by the contents of the hold, particularly if the contents are powdered, dusty, or liquid in form. To aid in dealing with this problem, there have been some instances where a wiper is applied to the inside face of the sight glass and operable by a T-handle or the like from the outside, to clear the glass. But the contents of the hold are sometimes very detrimental to the material used in the wiper. A material somewhat resistant to one type of chemical, may be very susceptible to attack by another type of chemical, necessitating repair on a more frequent than desirable basis. Also, because of the way that sight glasses are normally mounted to decks sealing them and maintaining a seal can be very difficult. The present invention is directed to reducing the difficulty in dealing with these problems.